Convert Snellen visual acuity to LogMAR, decimal, and MAR. Check driving eligibility and compare vision classification across international standards.
The 20/20 Vision Calculator converts Snellen acuity into LogMAR, decimal acuity, and Minimum Angle of Resolution (MAR). It also compares the result with common driving thresholds and the usual legal-blindness cutoff.
Snellen notation expresses the test distance and the line that was read. For example, 20/40 means the chart line was read at 20 feet when a person with typical acuity could read it at 40 feet.
That makes it easier to compare eye-test results that are written in different formats.
Seeing visual acuity in several formats makes it easier to compare eye exams, driving requirements, and research notation. The same reading can look different depending on whether it is written as Snellen, LogMAR, decimal acuity, or MAR.
LogMAR = log₁₀(Snellen denominator / 20) Decimal Acuity = 20 / Snellen denominator MAR = Snellen denominator / 20 (arcmin) Corrected Snellen at distance d: 20/(denom × 20/d)
Result: Right: LogMAR 0.10, Left: LogMAR 0.18 — Near Normal vision, meets driving requirement
Both eyes are slightly below 20/20 but well within the 20/40 US driving threshold. At age 45, this is within normal range.
Visual acuity is typically the first test performed in any eye examination. The Snellen chart, invented by Dutch ophthalmologist Herman Snellen in 1862, remains a widely used reference system. Modern eye care also uses notation systems including LogMAR, decimal acuity, and MAR, each with advantages for different clinical and research contexts.
While this calculator helps interpret your numbers, certain findings warrant prompt professional attention. A sudden drop in acuity in one eye could indicate retinal detachment, macular degeneration, or vascular occlusion. A difference of three or more lines between eyes (anisometropia) may affect binocular function. Any acuity below 20/40 that hasn't been evaluated should prompt an eye exam, especially for drivers.
Mild refractive errors (20/25 to 20/40) are typically correctable with glasses, contacts, or refractive surgery. Moderate errors (20/50 to 20/80) usually respond well to correction but may indicate underlying conditions. Severe low vision (20/100+) often requires specialized low-vision aids, magnification devices, and rehabilitation services beyond standard correction.
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This page converts the entered Snellen fraction into decimal acuity, MAR, and LogMAR using standard visual-acuity relationships. The driving and legal-blindness notes are broad reference markers only and are not a substitute for the current rules in a specific state or country.
It is best used as a notation-conversion and interpretation aid after an eye exam, not as a stand-alone eye-health assessment. Visual acuity is only one part of vision, and this page does not assess visual field, contrast sensitivity, ocular disease, or refraction.
20/20 means you can see at 20 feet what a person with normal vision sees at 20 feet. It is the baseline for "normal" acuity but not perfect — some people achieve 20/15 or even 20/10.
No. 20/20 is the standard baseline. Many people, especially younger individuals, can see 20/15 or 20/10. "Perfect" vision also requires good contrast sensitivity, color vision, and peripheral vision.
LogMAR (Logarithm of the Minimum Angle of Resolution) provides a linear scale for statistical analysis. A LogMAR of 0 equals 20/20; negative values are better than 20/20; positive values are worse.
Most US states require 20/40 or better in at least one eye, with or without correction. Some states allow 20/50 or 20/60 with restrictions like daylight-only driving.
In the US, legal blindness is generally defined as best-corrected visual acuity of 20/200 or worse in the better eye, or a visual field of 20 degrees or less.
Age-related acuity decline (presbyopia) typically begins around age 40 for near vision. Distance acuity may decline after age 60, with 20/25 to 20/30 being common in healthy older adults.
Snellen uses 20 feet (US) while metric uses 6 meters. 20/20 equals 6/6. To convert, divide both numbers by 3.28 (feet to meters).